Create New Mission Category?

I'd like to create a new Category for Missions, such as the "Backcountry", "Pilot for Hire", etc. Categories. (Just creating a new folder within The Missions folder won't do it.). Anybody know how to do this?

BTW, I'm not looking for ways to write some C++, or whatever, routine to do this. I'd just like to know if there's any simple way to add another Category or some workaround, e.g. creating a separate category within some existing category, etc.

Thanks!